The invention relates to a kit for an internal fixing device, particularly for the fixation of vertebrae, which includes a counterclockwise thread and/or a clockwise thread.
Such fixing devices serve primarily for the internal fixation of defects in the thoracic and lumbar parts of the spine.
Due to their small size, the implantation of conventional fixing devices requires a high degree of skill and experience on the part of the implanting surgeon. Under surgery conditions, in particular, it is difficult to determine whether the parts of the kit or the threaded connections on these parts have counterclockwise or clockwise threads. Differentiation between a clockwise thread region and a counterclockwise thread region can often only be made by experimentally screwing on the screw cap.
To ensure sufficient stressability for the fixing device it is also necessary that the regions provided with external threads are screwed in to a minimum depth. Such depth, however, cannot be estimated since the total length of the external threads differs. However, when such a fixing device is set for the patient, knowledge of the minimum screw-in depth required is absolutely necessary, so that the element provided with the external thread will not inadvertently separate from the corresponding element provided with an internal thread and thus endanger the fixation.
Since the surfaces of known implants are configured uniformly with respect to their optical reflection properties, there are no regions which could serve as identification.